Effects of trapping and subsequent short-term confinement stress on plasmacorticosterone in the brown treesnake (Boiga irregularis) on Guam

The effects of capture in a live trap and subsequent handling stress on pla sma concentrations of corticosterone and other sex steroids were examined i n wild male and female brown treesnakes (Boiga irregularis), an introduced species on Guam that has been implicated in the extirpation or decline of m any of that island's vertebrate species. Males and females that spent 1 nig ht in a trap had plasma levels of corticosterone about four and two times h igher, respectively, than those of the respective free-ranging controls. Me an plasma levels of corticosterone of snakes that had spent 3 nights in a t rap were intermediate between, but not significantly different from, those of snakes that had spent 1 night in a trap and free-ranging snakes, suggest ing that some acclimation to capture occurred during this period. Snakes th at were taken from traps and held in collecting bags for 10 min and 2 h pri or to blood sampling had levels of corticosterone about two and three times higher, respectively, than those of control snakes that were taken from tr aps and bled immediately. Concentrations of plasma corticosterone in free-r anging females were about two times higher than those of males but were wel l within the range of basal levels observed in other reptiles. Few snakes o f potential reproductive size were reproductive (males: 1 of 35; females: 2 of 33), and plasma concentrations of testosterone and progesterone in nonr eproductive males and females, respectively, were accordingly low. The poss ible relationship between corticosterone and these sex steroids, therefore, could not be adequately assessed, although there was a positive relationsh ip between plasma progesterone and corticosterone in the nonreproductive fe males. Nonetheless, as a prerequisite for studies on the seasonal hormonal cycles of this species on Guam, our observations raise the possibility that the stress caused by trapping could affect the levels of other sex steroid s and that, therefore, such studies should use free-ranging individuals. (C ) 2001 Academic Press.